Glucose is the main fuel of the human brain. However, which impact the glycemic index of lunch has on cognitive performance is not clear. A recently published review by Philippou and Constantinou suggested cautiously that a low-GI meal may favor cognitive functions in adults, but note that their findings are inconclusive due to differences in study design, study sample (e.g. size, age), time of testing and the cognitive domain being examined. Because of cerebral particularities, children may react highly sensitive to variations of glycose supply. Therefore, an optimised composition of meals at favourable mealtime should be considered for optimal cognitive performance. The increasing implementation of all-day schools in Germany requires the children's catering for lunch at school.